The human body contains many tubes of varied sizes, for example, in the circulatory, digestive, reproductive, respiratory and urologic systems. Numerous devices have been developed to allow inspection and manipulation of these tubes and surrounding structures. Minimally invasive techniques use devices that are externally inserted and designed to travel within these tubes. In the vast spectrum of disease, there is often a need to direct, for example, a needle, guidewire, stent, drainage or visualization device at an angle that differs from the path of the tube through which the instrument is passed.
Previous descriptions of catheter delivery systems that direct wire-like devices at angles other than substantially parallel to the pathway of the tube through which the delivery system is traveling can be divided into either external steerable devices or internal deflection devices. External steerable devices generally consist of long tubes made of flexible materials with a distal end controlled by an internally placed control wire. Traction or tension on the wire causes a torque on the distal end of the steerable catheter, which causes the distal end to be projected at an angle different than the proximal end. Hence, the distal end is steered by torque forces formed by pulling on a control wire, and portions of the entire instrument bend toward the direction of these forces. Internal deflection devices are straight or slightly curved tubes that have a side port near the distal end that rely on a fixed internal collision with a fixed internal deflection device. As a wire device passes through the tube, it collides with the fixed internal deflection device and is deflected at a fixed angle out a side port.
Attempts have been made to create functional external steering catheters as described above. Examples of these devices are described in: U.S. Pat. Nos. 4,582,181, 4,998,917, 5,439,006, and 6,126,649. These devices share common weaknesses, the most obvious being that these instruments, when flexed, no longer maintain a low-profile. These devices would not be able to achieve an adequate degree of angulation inside of a delicate fixed space such as, for example, a blood vessel or other delicate biological or non-biological space without the danger of accidentally injuring or compromising the walls of the space.
As mentioned, these devices generally have a wire that is pulled, which flexes the delivery system and causes the distal port to project at an angle different than the proximal port. A problem arises with this kind of steerable catheter-type device when the distal tip of the device flexes at an angle because such movement can project the distal wall of the device outside the narrow passageway of the tube or space accommodating the delivery system. When the distal end of the steerable catheter is aligned with the proximal end, as it would be for insertion, the device can fit safely inside of a small lumen tube or space. However, as the distal end of the steerable catheter is torqued and consequently bent at an angle by the tensioning of a control wire or movement of a steering apparatus, such movement distorts the path and arc of the steerable catheter in such a way that it no longer fits inside of the small tube or space it was designed to manipulate or in which it was designed to operate. That is, as the distal tip or the steerable catheter is steered, the distal tip is no longer aligned with the proximal tip. Consequently, a vessel or space that could safely accommodate such an instrument would need to be at least as wide as the proximal port, where the instrument is actually inserted, and as wide as the distal tip when bent at the desired angle for delivery. As a steerable delivery system transforms from a linear tube to a bent tube, sheering forces can place the entire length of the biological tube or the non-biological space at a high risk of injury. The tip itself, when turned and projected outside the path of the remainder of the delivery system, would generate a high risk of focal perforation.
Attempts have been made to design internal deflecting cannulas. Generally these catheters have side guidewire exit ports located proximal to their distal tips. Examples of these devices are described in U.S. Pat. Nos. 4,405,314, 4,947,864, 5,183,470, 5,190,528, 5,413,581, 5,464,395 and 6,511,458. These designs also share common weaknesses. First, internal deflection devices are not adjustable, i.e., deflection can be achieved only at one angle. The lack of an adjustable internal deflection device disallows the use of a guidewire to be used down a straight pathway to place the device in the desired location. Efforts to overcome this weakness by having two separate lumens, one with an internal deflection device and the other with a straight lumen for placement of the catheter such as U.S. Pat. No. 5,655,548 are lacking, in part because the need to accommodate multiple lumens doubles the width of the delivery system. Such devices are also not adjustable. Moreover, the narrow spaces in which such systems are used limits the angle at which a wire or catheter can be deflected.
Another major weakness shared by both external steerable and internal deflecting delivery systems is that while deploying a device such as, for example, a stent at an angle is possible, removing the external steerable or internal deflecting delivery system with the stent in proper position is exceedingly difficult and impossible at angles approaching right-angles to the device passageway. Such problems obviate any practical use of these devices as means of deploying devices, such as, for example, stents and drainage catheters, at lasting angles. Attempts to remove the external steerable or internal deflecting delivery system in a linear path, cause collisions between the distal end of delivery system and the delivered device, when placed at an angle that differs from the linear path of delivery system removal.
The collision problems that arise with removal of external steerable delivery systems lie in the fact that once a device, such as a stent or wire, has been placed, the delivery system must conform to the shape of the lumen or space in order to be removed from the lumen or space. That is, as the device is withdrawn along the path of the lumen, the external shape of the delivery device must conform to the lumen or space geometry. Any effort to remove the catheter delivery system in its “bent,” or device delivery, form would cause the distal end, i.e. the end with the deployed device, to deform to the shape of the lumen geometry. Thus any attempts to remove the delivery system with a device, such as a stent or guide-wire, placed at an angle would cause dislodgement of the device as the axis of the forces necessary to remove the delivery system differ from the angle of device placement.
Multiple problems arise with removal of internal deflection delivery devices as well. An obvious problem is seen in U.S. Pat. No. 6,514,217, which relates to an internal deflection device that relies on a flapper assembly to direct a catheter. This assembly uses an internal deflection device just distal to the external slot. Because the internal deflection of the delivered device must be fixed in a location for a flapper device to function, if the operator attempts to remove the internal deflection delivery system from the body by pulling proximally along the length of the tube, the internal deflection device would collide with the wire or stent, which is projected at an angle different from that of the tube. Consequently, as the delivery system is withdrawn from the body by pulling proximally along the length of the tube, the wire or stent at an angle different from that of the tube would also be pulled along the angle of the tube. This pulling force would tear and disrupt the surrounding tissues and ultimately the wire or stent would be pulled out of the body along with the delivery system causing great damage.
Thus, external steerable or internal deflection delivery devices have many limitations inherent in their design leaving a need for a device that can fully function in a narrow biological or non-biological space, deploy a variety of separate and lasting devices such as, for example, stents, drainage catheters and visualization devices, at accurate angles and control these angles of deployment in a user-definable manner. These devices also leave the need for an adjustable device delivery system that can be withdrawn from the delivery area after the placement of one or more devices at a user-defined angle without disruption of these devices from their desired location.